Conventionally, in a liquid crystal display device, for the purpose of improving display quality of liquid crystal panels having a large number of pixels and a high aperture ratio which increase with each passing year, there have been developed various methods for driving picture elements in a liquid crystal panel. Out of such various driving methods, alternate current (AC) driving includes frame reversal driving, line reversal driving, and dot reversal driving. Also, a combination of these driving methods can be used.
Usually, a liquid crystal panel has a plurality of picture elements arranged in a matrix manner, a gate bus line provided for each row for selecting each row of picture elements, and a source bus line provided for each column for supplying a data signal to each column of picture elements. The picture elements are driven in such a manner that (i) while the source bus lines are supplied with data signals, a gate bus line is scanned and thereby picture elements are selected and (ii) the data signals are applied to these selected picture elements. Such an operation of driving picture elements is common to various driving methods.
Meanwhile, in order to suppress a deterioration of picture elements, a data signal applied to the picture elements is switched between a positive polarity and a negative polarity relative to a common electric potential. In particular, dot reversal driving is known to be good for improving image quality. This is because the dot reversal driving causes a data signal applied to a picture element to have a polarity reverse to those of adjacent picture elements located on the upper, lower, right and left sides, thereby achieving stable input of picture element electric potentials.
Note however that, in the dot reversal driving, since a period in which an electric potential of each source bus line is rewritten is shortened as a scanning speed increases, a problem occurs in which the picture elements are not sufficiently charged. Further, in view of power consumption, it is desired that this period be long.
Under such circumstances, for example, Patent Literature 1 describes a technique of carrying out driving that looks like dot reversal driving, by arranging pixels so that they are alternately connected to source bus lines. According to the technique, (i) one (1) source bus line is added so that pixels in each column are connected one-by-one alternately to an adjacent source bus line located on their left side and an adjacent source bus line located on their right side and (ii) data signals are supplied to the source bus lines such that a polarity is the same between pixels adjacent to each other in a row direction, polarities of pixels adjacent to each other in a column direction are reverse to each other, and such polarity relation is reversed for every one (1) field. This makes it possible to carry out driving that looks like dot reversal driving, while causing each source bus line to have the same polarity over one (1) field period.